Garai Coliseum still very easy for duo, except for large HP of sriosian he is not that tough, he attacks only the player with large threat near him and second player just keep healing and throwing fireballs.. no other distraction except those magical traps or what ever you call, the scorpion is like 5x times stronger than sriosinan.
I would suggest adding to him some ability to cast more spells and summon the small scorpions etc which will get more distraction and harder to survive, which i believe it will be way more fun

